To protect national and public security and interests, under the authorization of law, the national security authority must implement lawful monitoring via public communications networks. For description purposes, lawful monitoring herein is described as monitoring. A monitoring system generally consists of a monitoring center and network elements. Network elements are communications devices providing communications services for users in a communications network (or network devices), such as a program controlled switch, a mobile switching center server (MSC server) in a mobile circuit switched network, and a gateway (GW). The monitoring center is an entity that receives monitoring commands from the national security authority and receives monitoring target related information reported by network elements.
An important function of monitoring is to monitor the current location of a monitoring target. When the location of the monitoring target changes, a network device must report the current location information of the monitoring target to the monitoring center. In an evolved packet system (EPS), a concept of tracking area (TA) and a TA list technique are adopted. A TA is a division of a radio coverage area. When an EPS allocates page areas for user equipment (UE, which is a monitoring target), the EPS may combine one or more adjacent TAs to a TA list and send the list to the monitoring target. The current TA of the monitoring target is included in the newly allocated TA list. When the monitoring target is idle, its location update is based on the TA list. When the monitoring target moves from a TA in the TA list to a TA outside the TA list (or when a periodic location update timer expires), the monitoring target will initiate a location update procedure and notify the network of its location.
During the implementation of the present disclosure, the inventor finds at least the following problem in the prior art:
When the monitoring target moves inside a TA, or moves from one TA in a TA list to another TA in the TA list, the monitoring target does not notify the network of the change of its location. As a result, the EPS network is unable to know more accurate location information of the monitoring target and the monitoring system is unable to obtain a continuous moving track of the monitoring target or the moving direction, distance and speed information of the monitoring target.